strdup的原理以及用法

#include <string.h>#include <stdio.h>#include <stdlib.h>char* strDUP(char* str){int len = strlen(str);if(len <=0 )return NULL;char* p = (char*)malloc(len+1);memset( p, 0, len+1);memcpy( p, str, len);return p;}int main(int argc, char* argv[]){char* str = "this is a demo for strdup()";char* p = strDUP(str);printf(p);printf("\n");free(p);return 0;}